1. Technical Field
The present invention relates to a magnetic element that is capable of generating only one skyrmion and erasing the generated one skyrmion, a skyrmion memory using the magnetic element, a skyrmion memory device using the magnetic element, a skyrmion-memory embedded solid-state electronic device, a data storage apparatus having a skyrmion memory embedded therein, a data processing apparatus having a skyrmion memory embedded therein, and a communication apparatus having a skyrmion memory embedded therein.
2. Related Art
A known magnetic element uses the magnetic moments of a magnet as digital information. The magnetic element has a nanoscale magnetic texture serving as a component of a non-volatile memory, which does not require electric power to maintain stored information. The magnetic element is expected to be used as a high-capacity information storage medium due to its advantages such as a very high density achieved by the nanoscale magnetic texture and becomes increasingly important as a memory device used in an electronic device.
As possible next-generation magnetic memory devices, magnetic shift registers are proposed mainly by IBM United States. Magnetic shift registers drive magnetic domain walls and transfer the configuration of the magnetic moments of the magnetic domain walls using currents to read stored information (see U.S. Pat. No. 6,834,005).
FIG. 28 is a schematic view showing the principle of how to drive magnetic domain walls using currents. The magnetic domain wall means the boundary between the magnetic regions having magnetic moments of opposing orientations. FIG. 28 uses the solid lines to show the magnetic domain walls in a magnetic shift register 1. By supplying currents flowing in the direction shown by the arrows to the magnetic shift register 1, the magnetic domain walls are driven. As a result of the movement of the magnetic domain walls, a magnetic change is caused according to the orientations of the magnetic moments positioned above a magnetic sensor 2. The magnetic change is detected by the magnetic sensor 2, which retrieves magnetic information.
The above-described magnetic shift register 1, however, requires large currents to move the magnetic domain walls. Another drawback of the above-described magnetic shift register 1 is a low transfer speed achieved by the magnetic domain walls. Accordingly, the magnetic shift register 1 suffers from slow memory writing and erasing.
In light of the above, the inventors of the present invention proposed a skyrmion sensor using as memory units skyrmions generated within magnets (see Japanese Patent Application Publication No. 2014-86470). By making such proposals, the inventors of the present invention disclosed that skyrmions can be driven by currents.
A skyrmion has an extremely small magnetic texture with a diameter of 1 nm to 500 nm and can maintain the structure for a long time. For these reasons, it is highly expected to use skyrmions as memory elements. The fundamental physical properties of skyrmions are increasingly known (see, Naoto NAGAOSA and Yoshinori TOKURA, “Topological properties and dynamics of magnetic skyrmions,” Nature Nanotechnology, United Kingdom, Nature Publishing Group, Dec. 4, 2013, Vol. 8, p 899-911). Here, Junichi IWASAKI, Masahito MOCHIZUKI, and Naoto NAGAOSA, “Current-induced skyrmion dynamics in constricted geometries,” Nature Nanotechnology, United Kingdom, Nature Publishing Group, Sep. 8, 2013, Vol. 8, p 742-747 reports that inventions are actually made by using skyrmions as memories. Iwasaki et al. discloses an invention directed to how to generate and erase skyrmions. However, the methods of generating and erasing skyrmions disclosed in Iwasaki et al. use steady-state currents. When steady-state currents is employed, a large number of skyrmions are generated. It has yet not been discovered how to use the continuously generated skyrmions as memory bits. If skyrmions are used as memories with steady-state currents, the power consumption significantly increase. Power is also required to maintain skyrmions as memories, which makes it impossible to practically use skyrmions as non-volatile memory. The above are the serious problems to be solved. In addition, the method of manufacturing a skyrmion memory is not disclosed. Furthermore, no circuits are disclosed. Thus, the above-mentioned documents do not disclose various technical issues that would arise to realize practical devices using skyrmions.